Last Updated on November 3, 2020
Have you ever attempted to leave for work in the morning, only to find that your automatic transmission is stuck in the park position? If so, you are certainly not alone. While indeed troubling, this issue is far more common than one might think.
Luckily, when a transmission is stuck in park, a minor mechanical fault is often to blame. Such an issue seldom requires extensive mechanical intervention or heavy repair to remedy. With a little prior knowledge and a few minutes worth of impromptu diagnostics, the root cause of this concern can be uncovered.
Read on to learn more about why your transmission is stuck in park, and what will be required to fix this condition.
Understanding Transmission “Park” Operation
Throughout the years, automotive manufacturers have made great strides toward increasing vehicle safety. As a result, automatic transmissions have been engineered to feature a number of fail-safe features, which prevent a vehicle from moving, other than when intended.
All automatic transmissions now rely upon a device called a parking pawl, to prevent unintended vehicle movement when in the “park” position. When a vehicle is placed in park, this lever-like device engages a specialized parking gear, which is mated to the transmission’s output shaft. The parking pawl disengages from this parking gear when any alternative shifter selection is made.
Potential Causes of a Stuck In Park Condition
The following are the most likely causes of a vehicle’s transmission failure to release from its park position.
#1 – Incline Induced Pawl Pressure
When parking on a steep incline, a transmission’s parking pawl can come under an immense amount of pressure, as it wedges into its corresponding parking gear.
Under these circumstances, the parking pawl and parking gear are supporting a vehicle’s entire weight. This often makes it difficult to shift out of the park position, leaving motorists stranded in the process.
In this case, one must relieve this pressure, in order to successfully shift into any drive gear. This often requires the help of a second individual, who can create enough movement to facilitate proper disengagement, by rocking the vehicle back and forth.
However, on steep inclines, this process might require the use of a secondary towing vehicle.
In order to prevent such a situation, it is imperative to set your parking brake when attempting to stop on an incline, prior to placing your vehicle in park. This places all weight on a vehicle’s parking brake assemblies, as opposed to the parking pawl and parking gear.
#2 – Shifter Interlock
To prevent a vehicle from being accidentally shifted into drive or reverse, engineers typically fit all vehicles with a shifter interlock system. This interlock manually bars a shifter from being moved out of the park position, until the vehicle’s brake pedal is depressed.
However, interlock systems do fail in the engaged position on occasion. To prevent motorists from becoming stranded under such circumstances, the majority of manufacturers fit their vehicles with a shift lock release. The use of this release allows a driver to override their vehicle’s shifter interlock.
The shifter interlock in some vehicles can be bypassed by simply turning your key to the accessory position, and placing the shifter in the neutral position, where the vehicle can then be started.
However, if this proves ineffective, one can access the manual shift lock override, which is typically engaged by inserting a key or small flathead screwdriver.
The location of this manual override differs from one vehicle to the next, though one can consult their owner’s manual for specifics. It is a wise idea to familiarize yourself with such procedures now, rather than to be forced to seek such information out when in the midst of a park related issue.
#3 – Brake Switch Failure
As previously mentioned, most vehicles feature a shifter interlock that is reliant upon brake pedal operation for disengagement. This system detects brake pedal operation through the actuation of a brake switch.
If this switch fails, the interlock function can be adversely affected. Typically, a vehicle’s shift interlock will act as if the brake pedal was never applied.
The simplest way to diagnose such an issue is to have a helper monitor your vehicle’s brake light operation. If your brake lights fail to illuminate when you depress the brake pedal, your vehicle’s brake switch is likely faulty. This is a presumptive diagnosis, which can later be verified through testing with a multimeter.
If your vehicle’s brake switch does indeed prove to be faulty, replacement will be necessary in order to prevent the recurrence of this issue.
In many cases, this is a relatively simple job to complete, and requires little to no expenditure outside of the purchase of a replacement sensor. Replacement brake sensors can typically be sourced from any local parts distributor.